[petsc-users] Data decomposition in PETsc for Poisson solver

[Michele Rosso]

Hi,

I need some help to use the PETSc library inside my Fortran 95 code.
My goal is to solve a symmetric linear system that derives from the 
finite difference discretization
of the Poisson equation. I will use the preconditioned conjugate method.

I am mostly interested in how to decompose my data among the different 
processes.
In particular:

1) Since my code already implements the 2D-decomposition, would it be 
best to build the matrix with the  DMDA object type, DA object type
      or the regular Mat type?

2) After inserting values into a vector/matrix, PETSc performs any 
needed message passing of nonlocal components, thus the values locally 
contained on a process  may be communicated to another process.  How can 
I revert this at the end of the computation, that is, how can I be sure 
that the local solution vector contains the values associated to the 
grid nodes contained into the hosting process?


Thank you,

Michele
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